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Close Similarity (close + similarity)
Selected AbstractsTesting long-term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, AustraliaBASIN RESEARCH, Issue 3 2007D. W. Maidment ABSTRACT Detrital zircon geochronology of Neoproterozoic to Devonian sedimentary rocks from the Georgina and Amadeus basins has been used to track changes in provenance that reflect the development and inversion of the former Australian Superbasin. Through much of the Neoproterozoic, sediments appear to have been predominantly derived from local sources in the Arunta and Musgrave inliers. Close similarities between the detrital age signatures of late Neoproterozoic sedimentary rocks in the two basins suggests that they were contiguous at this time. A dominant population of 1.2,1.0 Ga zircon in Early Cambrian sediments of the Amadeus Basin reflects the uplift of the Musgrave Inlier during the Petermann Orogeny between 560 and 520 Ma, which shed a large volume of detritus northwards into the Amadeus Basin. Early Cambrian sedimentary rocks in the Georgina Basin have a much smaller proportion of 1.2,1.0 Ga detritus, possibly due to the formation of sub-basins along the northern margin of the Amadeus Basin which might have acted as a barrier to sediment transfer. An influx of 0.6,0.5 Ga zircon towards the end of the Cambrian coincides with the transgression of the Larapintine Sea across central Australia, possibly as a result of intracratonic rifting. Detrital zircon age spectra of sedimentary rocks deposited within this epicontinental sea are very similar to those of coeval sedimentary rocks from the Pacific Gondwana margin, implying that sediment was transported into central Australia from the eastern continental margin. The remarkably consistent ,Pacific Gondwana' signature of Cambro-Ordovician sediments in central and eastern Australia reflects a distal source, possibly from east Antarctica or the East African Orogen. The peak of the marine incursion into central Australia in the early to mid Ordovician coincides with granulite-facies metamorphism at mid-crustal depths between the Amadeus and Georgina basins (the Larapinta Event). The presence of the epicontinental sea, the relative lack of a local basement zircon component in Cambro-Ordovician sedimentary rocks and their maturity suggest that metamorphism was not accompanied by mountain building, consistent with an extensional or transtensional setting for this tectonism. Sediments deposited at ,435,405 and ,365 Ma during the Alice Springs Orogeny have detrital age signatures similar to those of Cambro-Ordovician sedimentary rocks, reflecting uplift and reworking of the older succession into narrow foreland basins adjacent to the orogen. [source] Modulation of spatial attention in a child with developmental unilateral neglectDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 4 2003Veronika B Dobler MD Attentional neglect of left space is one of the most striking acquired neurological disorders of adulthood. Recent evidence indicates a link between left spatial neglect and general right-hemisphere impairments in sustained attention and alertness. Poor sustained attention and alertness is also a central feature of other disorders, particularly childhood attention-deficit-hyperactivity disorder (ADHD). Here we present the case of a 7-year-old male showing that frank neglect can be present in children with sustained attention problems without a clear aetiological event, or obvious structural brain abnormalities as indicated by a normal MRI. Experimental amelioration of the neglect through left-hand movement and externally alerting stimulation by uninformative sounds further suggest close similarities to the adult disorder. We suggest that such distortions of spatial attention may be more common in childhood than previously thought. [source] HLA allele and haplotype frequencies in the Albanian population and their relationship with the other European populationsINTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 6 2009G. Sulcebe Summary Human leucocyte antigen (HLA) alleles are very interesting markers in identifying population relationships. Moreover, their frequency distribution data are important in the implementation of donor,recipient registry programs for transplantation purposes and also in determining the genetic predisposition for many diseases. For these reasons, we studied the HLA class I and II allele and haplotype frequencies in 160 healthy, unrelated Albanian individuals originating from all regions of the country. The HLA genotyping was performed through a 2-digit resolution SSOP method. The data were analysed with Arlequin and Phylip programs. No deviation was found from the Hardy,Weinberg equilibrium. A total of 17 A*, 30 B*, 12 Cw*, 13 DRB1* and 5 DQB1* alleles were identified. The six most frequent HLA-A-B-DRB1 haplotypes were A*02,B*18,DRB1*11 (5.60%), A*02,B*51,DRB1*16 (4.74%), A*01,B*08,DRB1*03 (3.48%), A*24,B*35,DRB1*11 (2.77%), A*02,B*51,DRB1*13 (2.21%), A*24,B*35,DRB1*14 (1.89%). Interestingly, 12 HLA-A-B-Cw-DRB1-DQB1 haplotypes occurred at a frequency >1%. When compared with the other populations, a close relationship was found with North Greek, Bulgarian, Macedonian, Romanian, Turkish, Cretan, Serbian, Croatian and Italian populations. A higher differentiation in allele frequency level was found with Western Europe populations. These data are the first report of HLA allele and haplotype distribution in an Albanian population inside this country. When compared with other populations, their distribution frequencies show close similarities with neighbouring populations of the entire Balkan area. [source] Peripheral synaptic contacts at mechanoreceptors in arachnids and crustaceans: Morphological and immunocytochemical characteristicsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2002Ruth Fabian-Fine Abstract Two types of sensory organs in crustaceans and arachnids, the various mechanoreceptors of spiders and the crustacean muscle receptor organs (MRO), receive extensive efferent synaptic innervation in the periphery. Although the two sensory systems are quite different,the MRO is a muscle stretch receptor while most spider mechanoreceptors are cuticular sensilla,this innervation exhibits marked similarities. Detailed ultrastructural investigations of the synaptic contacts along the mechanosensitive neurons of a spider slit sense organ reveal four important features, all having remarkable resemblances to the synaptic innervation at the MRO: (1) The mechanosensory neurons are accompanied by several fine fibers of central origin, which are presynaptic upon the mechanoreceptors. Efferent control of sensory function has only recently been confirmed electrophysiologically for the peripheral innervation of spider slit sensilla. (2) Different microcircuit configuration types, identified on the basis of the structural organization of their synapses. (3) Synaptic contacts, not only upon the sensory neurons but also between the efferent fibers themselves. (4) Two identified neurotransmitter candidates, GABA and glutamate. Physiological evidence for GABAergic and glutamatergic transmission is incomplete at spider sensilla. Given that the sensory neurons are quite different in their location and origin, these parallels are most likely convergent. Although their significance is only partially understood, mostly from work on the MRO, the close similarities seem to reflect functional constraints on the organization of efferent pathways in the brain and in the periphery. Microsc. Res. Tech. 58:283,298, 2002. © 2002 Wiley-Liss, Inc. [source] The auditory system of last instars in Gryllus bimaculatus DeGeerPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2009ERICH M. STAUDACHER Abstract Aspects of the auditory development of Gryllus bimaculatus are compared with those of other Orthopterans and Mantodea. Auditory receptor cell branching patterns and first-order auditory interneurones of last-instar crickets are morphologically very similar to adult cells; auditory thresholds are 30,45 dB higher in last instars than in adults; the ears of most ultimate nymphs lack directionality; and the tympana of last instars are not set apart clearly from the surrounding cuticle, are still thick, backed by a thick layer of epithelium, and lack microtrichia. Thus, the development of the auditory system from last-instar to adult shows close similarities between G. bimaculatus and Teleogryllus commodus but not to other Orthopteran or Mantid species. This supports the hypothesis that the pattern of post-embryonic development of the auditory system in crickets differs significantly from that in other Orthopterans and in Mantodea. [source] Cytology, palynology, and taxonomy of Asteropyrum and four other genera of RanunculaceaeBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2006QIONG YUAN A karyomorphological study of two species in Asteropyrum (Ranunculaceae) and five in presumably related genera (one each in Caltha, Coptis, and Dichocarpum and two in Thalictrum) reveals close similarities between Asteropyrum and Caltha, but obvious differences between Asteropyrum and Coptis, Dichocarpum, and Thalictrum, in some karyological features, such as the structure of the interphase nuclei, chromosome size, basic chromosome number, and condensation behaviour of chromosomes during the mitotic prophase. The chromosomes of Asteropyrum are categorized as being of the R-type and the basic chromosome number is confirmed as x = 8, indicating a possible close affinity of Asteropyrum to members in the subfamily Helleboroideae, in particular to Caltha and its allies. Asteropyrum peltatum and Asteropyrum cavaleriei are shown to be more or less differentiated from each other in gross morphology and palynology, and somewhat independent in geographical distribution, albeit with intermediate forms occurring where their distribution zones overlap. It seems justifiable to treat them as two subspecies of A. peltatum. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 152, 15,26. [source] Strong Evidence for an Unprecedented Borderline Case of Dissociation and Cycloaddition in Open-Shell 1,3-Dipole Chemistry: Transient Nitrilium Phosphane-Ylide Complex Radical CationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009Holger Helten Abstract The reaction of 3-ferrocenyl-substituted 2H -azaphosphirene complexes 1a,c in the presence of substoichiometric amounts of ferrocenium hexafluorophosphate yields 3,5-diferrocenyl-substituted 2H -1,4,2-diazaphosphole complexes 3a,c and difluoro(organo)phosphane complexes 4a,c. The reaction of 1a,c and [FcH]PF6 with cyanoferrocene yields 3a,c in a straightforward way. The molecular structures of 3a,c were unambiguously identified by multinuclear NMR spectroscopic experiments, mass spectrometry, and single-crystal X-ray diffraction studies. DFT calculations on model complexes 1d,m and 3d,m reveal a close similarity of Mo and W complexes (vs. Cr) and a strong influence of the ferrocenyl substituent on the geometry, spin, and charge distribution of reactive intermediates and the reaction course. Strong support for the assumption of a dissociation,cycloaddition reaction sequence leading to 3 and thus a surprising "cannibalistic" reaction was obtained.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Comparison of DNA Complex Formation Behaviour for Two Closely Related Lexitropsin AnaloguesHELVETICA CHIMICA ACTA, Issue 5 2009Abstract Two closely related lexitropsin analogues that differ only in the form of the ,headgroup' functionality (CHO (for 1) vs. Ac (for 2)) have been studied in their DNA-binding capacity for the sequence d(GCATATATGC) using 1H-NMR spectroscopy. DNA-Complex formation for the CHO derivative was apparent from the observation of new NMR signals on titration of DNA with ligand. Detailed investigation and assignment of the data for a ligand/DNA-duplex ratio of 2,:,1 clearly delineated the structure as one associated with the ,minor groove' class of DNA complexes. The structure of the complex was determined on the basis of the acquired NMR data. Features characteristic of typical 2,:,1 minor-groove complexes were apparent. In a similar experimental approach, the Ac analogue ligand,DNA binding response was investigated. Despite the close similarity in chemical structure to the CHO case, the Ac analogue was found to produce NMR data of a much poorer quality. This was attributed to more rapid on/off chemical exchange equilibrium between ligand and DNA. From close analysis and comparison of the NMR data for the ,Ac' and ,CHO' headgroup ligand,DNA complexes, it was possible to ascertain that the same type of complex formed in each case but with different relative binding constants. Consideration of the nature and form of these complexes has been made with reference to a previously determined structure from our laboratory for the related lexitropsin analogue thiazotropsin A. [source] An extended Huygens' principle for modelling scattering from general discontinuities within hollow waveguidesINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2001Ronald L. Ferrari Abstract The modal fields, generalized scattering matrix (GSM) theory and dyadic Green's functions relating to a general uniform hollow waveguide are briefly reviewed in a mutually consistent normalization. By means of an analysis linking these three concepts, an extended version of the mathematical expression of Huygens' principle is derived, applying to scattering from an arbitrary object within a hollow waveguide. The integral-equation result expresses the total field in terms of the incident waveguide modal fields, the dyadic Green's functions and the tangential electromagnetic field on the surface of the object. It is shown how the extended principle may be applied in turn to perfect conductor, uniform material and inhomogeneous material objects using a quasi method of moments (MM) approach, coupled in the last case with the finite element method. The work reported, which indicates how the GSM of the object may be recovered, is entirely theoretical but displays a close similarity with established MM procedures. Copyright © 2001 John Wiley & Sons, Ltd. [source] First identification of an ancient Egyptian mummified human placentaINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1 2005A.-M. Mekota Abstract In the course of excavations at Thebes-West, Upper Egypt, a human organ was recovered from the poorly preserved torso of a female mummy, which was archaeologically dated to the New Kingdom. In the field, the organ was tentatively identified as a liver, but without much certainty. After rehydration and fixation, histological observations led to a rejection of this diagnosis and resulted in the hypothesis that this organ could be a placenta. Comparative histology, performed on an experimentally mummified modern human placenta, revealed a close similarity of microstructural features, which strongly supports the diagnosis of the organ as a placenta. In this paper, we can therefore present the first report of an ancient Egyptian mummified human placenta and provide new insight into Egyptian funeral practices in general, and the fate of the excavated female in particular. Copyright © 2004 John Wiley & Sons, Ltd. [source] Yttrium oxide (Y2O3) as an inert marker in digestibility studies with dogs, blue foxes and mink fed diets containing different protein sourcesJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 9-10 2007S. G. Vhile Summary The study evaluated the use of yttrium oxide (Y2O3) as an inert marker in studies of apparent total tract digestibility in dogs, blue foxes and mink. Comparison was made with total faecal collection, and use of chromic oxide (Cr2O3) as marker respectively. Four experimental diets were added 0.1 g/kg yttrium oxide and 10 g/kg chromic oxide and fed to four animals of each species. Faecal recovery of yttrium oxide was 94.4% (SEM ± 1.0), and of chromic oxide 105.8% (SEM ± 1.5). The digestibilities of dry matter, crude protein, crude fat, starch and total carbohydrates obtained by total collection and yttrium oxide as marker showed close similarity, and in most cases not significant differences, independent of species and diets. In dogs, overall digestibilities of main nutrients with chromic oxide as marker were not significantly different from overall means obtained with yttrium oxide (p > 0.05). Overall digestibility of dry matter, crude protein and total carbohydrates in blue foxes and mink was significantly higher with chromic oxide than with yttrium oxide (p < 0.05). In dogs and blue foxes, digestibilities of individual amino acids determined by use of yttrium oxide were not different from values obtained using total collection of faeces, both within diets and for overall mean (p > 0.05). Overall amino acid digestibilities in dogs determined with chromic oxide as marker were similar to corresponding figures for yttrium oxide, whereas use of chromic oxide resulted in significantly higher digestibilites for a number of amino acids compared with yttrium oxide in foxes and mink (p < 0.05). The digestibilities of most main nutrients and amino acids revealed no interaction between diet and method (p > 0.05). The study showed that yttrium oxide can be used in low concentration in the feed, and allows high accuracy of analyses and thereby precise digestibility determination. It is concluded that yttrium oxide is an alternative inert marker to chromic oxide in the studied species. [source] Genetic heterogeneity and functional properties of intestinal bifidobacteriaJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2004J. Mättö Abstract Aims:, The aim of the present study was to compare several molecular methods for the identification and genotyping of bifidobacteria, and further to investigate genetic heterogeneity and functional properties of bifidobacterial isolates from intestinal samples of Finnish adult subjects. Methods and Results:, A total of 153 intestinal bifidobacterial isolates were included in initial screening and 34 isolates were further characterized. Identification results obtained with PCR,ELISA and ribotyping were well in accordance with each other, while randomly amplified polymorphic DNA (RAPD) gave tentative identification only to Bifidobacterium bifidum and to 65% of the B. longum isolates. The most commonly detected species were B. longum biotype longum followed by B. adolescentis and B. bifidum. In addition, B. animalis (lactis), B. angulatum and B. pseudocatenulatum were found. Ribotyping and pulsed-field gel electrophoresis (PFGE) proved to be discriminatory methods for bifidobacteria, but also RAPD revealed intraspecies heterogeneity. Besides two B. animalis (lactis) isolates with very close similarity to a commercially available probiotic strain, none of the intestinal isolates showed optimal survival in all tolerance (acid, bile and oxygen) or growth performance tests. Conclusions:, Several species/strains of bifidobacteria simultaneously colonize the gastrointestinal tract of healthy Finnish adults and intestinal Bifidobacterium isolates were genetically heterogeneous. Functional properties of bifidobacteria were strain-dependent. Significance and Impact of the Study:, Applicability of ribotyping with the automated RiboPrinter® System for identification and genotyping of bifidobacteria was shown in the present study. [source] Use of real-time gene-specific polymerase chain reaction to measure RNA expression of three family members of rat cytochrome P450 4AJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 3 2001Kimberly B. Bleicher Abstract Exposure of rats to peroxisome proliferators induces members of the cytochrome P450 4A (CYP4A) family. In rats, the CYP4A family consists of four related genes, CYP4A1, CYP4A2, CYP4A3, and CYP4A8. We are specifically interested in examining CYP4A1, CYP4A2, and CYP4A3, each of which is expressed in a tissue-dependent and sex-dependent manner. While CYP4A1 is sufficiently different from the other two members to enable relatively easy specific quantitation, the close similarity between CYP4A2 and CYP4A3 makes quantitative discrimination difficult. We have combined a fluorescent real-time PCR assay (TaqMan®) with the sequence-specific mismatch amplification mutation assay (MAMA) to allow us to carry out specific quantitation of all three members of this family. The assay is designed such that a single fluorescent TaqMan® probe binds to all three gene products, while specificity is conferred by sequence-specific primers. This specific MAMA technique takes advantage of the ability of Taq polymerase to distinguish between the two cDNAs based on mismatches at the 3, end of a PCR primer. In the 84-base PCR product used for this assay, there is only a single-base difference between CYP4A2 and CYP4A3. Despite this similarity, there is at least a 1000-fold discrimination between the two sequences, using CYP4A2 or CYP4A3 specific standards. Analysis of rat liver RNA from both sexes demonstrates that this discrimination is also achieved in complex RNA mixtures. This technique should be broadly applicable to other areas of research such as allelic discrimination, detecting mutational hotspots in tumors, and discrimination among closely related members of other gene families. © 2001 John Wiley & Sons, Inc. J Biochem Mol Toxicol 15:133,142, 2001 [source] Calculation of sliding power loss in spur gear contactsLUBRICATION SCIENCE, Issue 1 2002Arto Lehtovaara Abstract An engineering-level calculation model for sliding power loss in spur gear contacts is presented. Teeth contact through the line of action is modelled as a constantly changing roller contact whose radius, speed, and load can be calculated from the gear geometry under the given operating conditions. The gear mesh cycle is approximated by a large number of elastohydrodynamic contacts. A constant film thickness and a Hertzian pressure distribution are assumed in each contact. The model includes non-Newtonian lubricant behaviour together with temperature and mixed lubrication effects in contact. The numerical solver is reasonably fast in evaluating effectively the sliding power loss dependence on the essential gear and lubricant parameters. The features and behaviour trends of the calculated sliding power losses have a close similarity with published results obtained from measurements and experiment-based power loss models with mineral oil. The limiting shear stress of the lubricant is observed to have an essential role in the power loss behaviour especially at high loads. [source] Density currents in shear flows: Effects of rigid lid and cold-pool internal circulation, and application to squall line dynamicsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 579 2002Ming Xue Abstract Idealized density current models that contain a rigid lid, developed in previous studies, are evaluated. It is shown, through numerical experiments, that a realistic stable layer placed at the level of the rigid lid acts very much like a rigid lid, in confining the environmental flow to the levels below and in controlling the behaviour of density currents that propagate in the flow. When this stable layer is replaced by a neutrally stable layer, the behaviour of the density current is very different. These results support the hypothesis that in the atmosphere, the tropopause or a tropospheric inversion layer acts much like a rigid lid in the idealized density current models, and the solutions of these models are applicable to organized quasi-two-dimensional convective systems such as squall lines in the atmosphere. The effects of cold-pool internal circulations on density current behaviour are also examined. When a single circulation is present initially inside the cold pool, the direction of circulation that gives rise to a smaller shear across the density interface leads to a smoother interface and a much more steady density current head. Large-amplitude eddies develop along the interface when the direction of circulation is reversed. When two layers of shear are initially present inside the cold pool, the flow pattern inside the cold pool tends to be dominated by the circulation of the lower layer. In this case, the behaviour of the density interface and density current head depends on more than just the initial cross-interface shear. The overall flow pattern in the density current, in which the cold-pool circulation contains rearward flows at the ground level, bears a close similarity to that found in mature squall line systems, as shown by comparisons with a simulated squall line. When the cold pool in a squall line is defined in terms of the equivalent potential temperature, the solutions of idealized density currents in sheared flows become more readily applicable to squall lines. Copyright © 2002 Royal Meteorological Society. [source] 4-Methoxy-1-naphthol: chains formed by O,H...O hydrogen bonds and ,,, stacking interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Bernard Marciniak The structure of 4-methoxy-1-naphthol, C11H10O2, (I), contains an intermolecular O,H...O hydrogen bond which links the molecules into a simple C(2) chain running parallel to the shortest crystallographic b axis. This chain is reinforced by intermolecular ,,, stacking interactions. Comparisons are drawn between the crystal structure of (I) and those of several of its simple analogues, including 1-naphthol and some monosubstituted derivatives, and that of its isomer 7-methoxy-2-naphthol. This comparison shows a close similarity in the packing of the molecules of its simple analogues that form ,-stacks along the shortest crystallographic axes. A substantial spatial overlap is observed between adjacent molecules in such stacks. In this group of monosubstituted naphthols, the overlap depends mainly on the position of the substituents carried by the naphthalene moiety, and the extent of the overlap depends on the substituent type. By contrast with (I), in the crystal structure of the isomeric 7-methoxy-2-naphthol there are no O,H...O hydrogen bonds or ,,, stacking interactions, and sheets are formed by O,H..., and C,H..., interactions. [source] 5-Amino-1-naphthol: two-dimensional sheets built up from R44(18) rings formed by O,H...N, N,H...O and ,,, interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Ewa Rozycka-Sokolowska The crystal structure of the title compound, C10H9NO, (I), contains intermolecular O,H...N and N,H...O hydrogen bonds which together form sheets parallel to the (001) plane containing rings with an unusual R44(18) motif. These rings are additionally stabilized by an intermolecular ,,, stacking interaction. The significance of this study lies in the comparison drawn between the molecular structure of (I) and those of related compounds (1,5-diaminonaphthalene, 8-amino-2-naphthol, 3-amino-2-naphthol and aniline), which shows a close similarity in the noncoplanar orientation of the amine group and the aromatic moiety. Comparison of the crystal structures of (I) and several of its simple analogues (1-naphthol, naphthalene-1,4-diol, naphthalene-1,5-diol and 4-chloro-1-naphthol) shows a close similarity in the packing of the molecules, which form ,-stacks along the shortest crystallographic axes with a substantial spatial overlap between adjacent molecules. [source] 4-Chloro-1-naphtholACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Ewa Rozycka-Sokolowska Molecules of the title compound, C10H7ClO, (I), are connected by a single strong O,H...O hydrogen bond into a simple C(2) chain, which runs parallel to the c axis and is additionally stabilized by intermolecular ,,, stacking interactions. The significance of this study lies in the comparison drawn between the crystal structure of (I) and those of several of its simple analogues. This comparison shows a close similarity in the packing of the molecules that form ,-stacks along the shortest crystallographic axes. A substantial spatial overlap is observed between adjacent molecules in such a ,-stack, depending mainly on the kind of substituent. [source] Structure of Staphylococcus aureus adenylosuccinate lyase (PurB) and assessment of its potential as a target for structure-based inhibitor discoveryACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2010Paul K. Fyfe The medium-resolution structure of adenylosuccinate lyase (PurB) from the bacterial pathogen Staphylococcus aureus in complex with AMP is presented. Oxalate, which is likely to be an artifact of crystallization, has been modelled in the active site and occupies a position close to that where succinate is observed in orthologous structures. PurB catalyzes reactions that support the provision of purines and the control of AMP/fumarate levels. As such, the enzyme is predicted to be essential for the survival of S. aureus and to be a potential therapeutic target. Comparisons of this pathogen PurB with the enzyme from Escherichia coli are presented to allow discussion concerning the enzyme mechanism. Comparisons with human PurB suggest that the close similarity of the active sites would make it difficult to identify species-specific inhibitors for this enyme. However, there are differences in the way that the subunits are assembled into dimers. The distinct subunit,subunit interfaces may provide a potential area to target by exploiting the observation that creation of the enzyme active site is dependent on oligomerization. [source] | ||||||||||||||||||||||